JP2022179327A - Substrate processing method and substrate processing apparatus - Google Patents

Abstract

To provide a technique of suppressing the poor shape of side walls of recesses during etching.SOLUTION: A substrate processing method in an exemplary embodiment is a method of processing a substrate including an etching target film and a mask having openings formed in the etching target film. The method includes steps of: (a) forming a first layer containing nitrogen on the side walls of recesses formed in the etching target film corresponding to the openings using first process gas; (b) forming, after the step (a), a second layer containing carbon and hydrogen over the first layer using second process gas that includes gas containing carbon and hydrogen; and (c) etching the recesses, after the step (b), using third process gas.SELECTED DRAWING: Figure 3

Description

Exemplary embodiments of the present disclosure relate to substrate processing methods and substrate processing apparatuses.

Patent Document 1 discloses a method of forming recesses in a silicon-containing film on a substrate by etching. In this method, the silicon-containing film is partially etched by an etching device. After that, a carbon-containing film is formed on the silicon-containing film by a film-forming apparatus without generating plasma. After that, the silicon-containing film is further etched by an etching device.

JP 2018-166223 A

The present disclosure provides a technique for suppressing shape defects of sidewalls of recesses during etching.

In one exemplary embodiment, a substrate processing method is provided. The method is a method for processing a substrate including a film to be etched and a mask provided on the film to be etched and having an opening, comprising: (a) recesses provided in the film to be etched corresponding to the openings; (b) after (a), using a second process gas containing a gas containing carbon and hydrogen; forming a second layer containing carbon and hydrogen on the first layer; and (c) after (b), etching the recess using a third process gas. .

According to one exemplary embodiment, it is possible to suppress shape defects of sidewalls of recesses during etching.

FIG. 1 is a schematic diagram of a substrate processing apparatus according to one exemplary embodiment. FIG. 2 is a schematic diagram of a substrate processing apparatus according to one exemplary embodiment. FIG. 3 is a flowchart of a substrate processing method according to one exemplary embodiment. FIG. 4 is a partially enlarged cross-sectional view of an example substrate. FIG. 5 is a cross-sectional view showing one step of a substrate processing method according to one exemplary embodiment. FIG. 6 is a cross-sectional view showing one step of a substrate processing method according to one exemplary embodiment. FIG. 7 is a cross-sectional view showing one step of a substrate processing method according to one exemplary embodiment. FIG. 8 is a partially enlarged cross-sectional view of an example substrate obtained by performing a substrate processing method according to one exemplary embodiment. FIG. 9 is a partially enlarged cross-sectional view of a substrate obtained by executing the substrate processing method in the first experiment. FIG. 10 is a partially enlarged cross-sectional view of a substrate obtained by executing the substrate processing method in the second experiment. FIG. 11 is a graph showing the thickness of the protective film obtained by executing the substrate processing method in each of the first experiment and the second experiment. FIG. 12 is a graph showing the thickness of the protective film obtained by executing the substrate processing method in the first, third to fifth experiments. FIG. 13 is a graph showing the relationship between the thickness of the protective film and the temperature obtained by executing the substrate processing method in the first, sixth to tenth experiments.

Various exemplary embodiments are described below.

In one exemplary embodiment, a substrate processing method is a method of processing a substrate including a film to be etched and a mask provided on the film to be etched and having an opening, comprising: (a) corresponding to the opening; (b) forming a nitrogen-containing first layer on a side wall of a recess provided in the etching target film using a first process gas; forming a second layer containing carbon and hydrogen on the first layer using a second process gas comprising a gas; and (c) after (b), using a third process gas, Etching the recess.

According to the method of the above embodiment, in (c), since the protective film is formed on the side wall of the recess, etching of the side wall of the recess is suppressed. Therefore, it is possible to suppress the shape defect of the side wall of the recess during etching.

The substrate processing method may further include repeating the steps (a) and (b) before the step (c). In this case, a thick protective film can be formed.

The substrate processing method may further include, after (c), repeating the steps (a), (b), and (c). In this case, deep recesses can be formed.

In at least one of (a) and (b), the temperature of the substrate may be less than 30°C. In this case, the protective film can be formed at a low temperature.

In (c) above, the temperature of the substrate may be less than 30°C. In this case, the recess can be etched at a low temperature.

In (c), plasma generated from the third processing gas may be used.

In (b), plasma generated from the second process gas may be used.

In (a), plasma generated from the first processing gas may be used.

The first layer may contain hydrogen.

The first layer may contain ammonia or a compound having an amino group.

The first process gas may contain a nitrogen-containing gas.

The second process gas may include at least one of hydrocarbon gas and hydrofluorocarbon gas.

The etching target layer may include at least one of a silicon-containing layer and a metal layer.

The substrate may be treated in-situ in (a), (b) and (c). In this case, throughput is improved. The substrate may be processed in-system in (a), (b) and (c).

In one exemplary embodiment, the substrate processing apparatus includes a chamber and a substrate support for supporting a substrate in the chamber, and the substrate includes an etching target film and an opening provided on the etching target film. and a gas supply configured to supply each of a first process gas, a second process gas and a third process gas into the chamber, the second process gas comprising: includes a gas supply section containing gas containing carbon and hydrogen, and a control section, wherein the control section supplies the second 1 process gas to control the gas supply to form a nitrogen-containing first layer, wherein the control unit supplies the second process gas after forming the first layer; to control the gas supply unit to form a second layer containing carbon and hydrogen on the first layer using a 3 is configured to control the gas supply to etch the recess using a process gas.

According to the apparatus of the above embodiment, in (c), since the protective film is formed on the side wall of the recess, etching of the side wall of the recess is suppressed. Therefore, it is possible to suppress the shape defect of the side wall of the recess during etching.

In one exemplary embodiment, a substrate processing method is a method of processing a substrate including a film to be etched and a mask provided on the film to be etched and having an opening, comprising: (a) a first processing gas containing the ( b) after (a), exposing the substrate to a second process gas, the second process gas comprising a carbon- and hydrogen-containing gas, wherein the carbon- and hydrogen-containing second layer is formed; and (c) after said (b), exposing said substrate to a third process gas, said third process gas being capable of etching said recess. , and a step.

According to the method of the above embodiment, in (c), since the protective film is formed on the side wall of the recess, etching of the side wall of the recess is suppressed. Therefore, it is possible to suppress the shape defect of the side wall of the recess during etching.

Various exemplary embodiments are described in detail below with reference to the drawings. In addition, suppose that the same code|symbol is attached|subjected to the part which is the same or equivalent in each drawing.

1 and 2 are diagrams schematically illustrating a substrate processing apparatus according to one exemplary embodiment. The substrate processing apparatus of this embodiment is, for example, a plasma processing system.

In one embodiment, a plasma processing system includes a plasma processing apparatus 1 and a controller 2 . The plasma processing apparatus 1 includes a plasma processing chamber 10 , a substrate support section 11 and a plasma generation section 12 . Plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas inlet for supplying at least one process gas to the plasma processing space and at least one gas outlet for exhausting gas from the plasma processing space. The gas supply port is connected to a gas supply section 20, which will be described later, and the gas discharge port is connected to an exhaust system 40, which will be described later. The substrate support 11 is arranged in the plasma processing space and has a substrate support surface for supporting the substrate.

The plasma generator 12 is configured to generate plasma from at least one processing gas supplied within the plasma processing space. The plasma formed in the plasma processing space includes capacitively coupled plasma (CCP), inductively coupled plasma (ICP), ECR plasma (Electron-Cyclotron-resonance plasma), and helicon wave excited plasma (HWP). ), or surface wave plasma (SWP: Surface Wave Plasma). Also, various types of plasma generators may be used, including AC (Alternating Current) plasma generators and DC (Direct Current) plasma generators. In one embodiment, the AC signal (AC power) used in the AC plasma generator has a frequency within the range of 100 kHz to 10 GHz. Accordingly, AC signals include RF (Radio Frequency) signals and microwave signals. In one embodiment, the RF signal has a frequency within the range of 200 kHz-150 MHz.

Controller 2 processes computer-executable instructions that cause plasma processing apparatus 1 to perform the various steps described in this disclosure. Controller 2 may be configured to control elements of plasma processing apparatus 1 to perform the various processes described herein. In one embodiment, part or all of the controller 2 may be included in the plasma processing apparatus 1 . The control unit 2 may include, for example, a computer 2a. The computer 2a may include, for example, a processing unit (CPU: Central Processing Unit) 2a1, a storage unit 2a2, and a communication interface 2a3. Processing unit 2a1 can be configured to perform various control operations based on programs stored in storage unit 2a2. The storage unit 2a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network).

A configuration example of the plasma processing system will be described below.
The plasma processing system includes a capacitively-coupled plasma processing apparatus 1 and a controller 2 . The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply section 20, a power supply 30 and an exhaust system 40. As shown in FIG. Further, the plasma processing apparatus 1 includes a substrate support section 11 and a gas introduction section. The gas introduction is configured to introduce at least one process gas into the plasma processing chamber 10 . The gas introduction section includes a showerhead 13 . A substrate support 11 is positioned within the plasma processing chamber 10 . The showerhead 13 is arranged above the substrate support 11 . In one embodiment, showerhead 13 forms at least a portion of the ceiling of plasma processing chamber 10 . The plasma processing chamber 10 has a plasma processing space 10 s defined by a showerhead 13 , side walls 10 a of the plasma processing chamber 10 and a substrate support 11 . The plasma processing chamber 10 has at least one gas supply port for supplying at least one processing gas to the plasma processing space 10s and at least one gas exhaust port for exhausting gas from the plasma processing space. Side wall 10a is grounded. The showerhead 13 and substrate support 11 are electrically insulated from the plasma processing chamber 10 housing.

The substrate support portion 11 includes a body portion 111 and a ring assembly 112 . The body portion 111 has a central region (substrate support surface) 111 a for supporting the substrate (wafer) W and an annular region (ring support surface) 111 b for supporting the ring assembly 112 . The annular region 111b of the body portion 111 surrounds the central region 111a of the body portion 111 in plan view. The substrate W is arranged on the central region 111 a of the main body 111 , and the ring assembly 112 is arranged on the annular region 111 b of the main body 111 so as to surround the substrate W on the central region 111 a of the main body 111 . In one embodiment, body portion 111 includes a base and an electrostatic chuck. The base includes an electrically conductive member. The conductive member of the base functions as a lower electrode. An electrostatic chuck is arranged on the base. The upper surface of the electrostatic chuck has a substrate support surface 111a. Ring assembly 112 includes one or more annular members. At least one of the one or more annular members is an edge ring. Also, although not shown, the substrate supporter 11 may include a temperature control module configured to control at least one of the electrostatic chuck, the ring assembly 112, and the substrate to a target temperature. The temperature control module may include heaters, heat transfer media, flow paths, or combinations thereof. A heat transfer fluid, such as brine or gas, flows through the channel. Further, the substrate support section 11 may include a heat transfer gas supply section configured to supply a heat transfer gas between the back surface of the substrate W and the substrate support surface 111a.

The showerhead 13 is configured to introduce at least one processing gas from the gas supply 20 into the plasma processing space 10s. The showerhead 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas introduction ports 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s through a plurality of gas introduction ports 13c. Showerhead 13 also includes a conductive member. A conductive member of the showerhead 13 functions as an upper electrode. In addition to the showerhead 13, the gas introduction part may include one or more side gas injectors (SGI: Side Gas Injectors) attached to one or more openings formed in the side wall 10a.

Gas supply 20 may include at least one gas source 21 and at least one flow controller 22 . In one embodiment, gas supply 20 is configured to supply at least one process gas from respective gas sources 21 through respective flow controllers 22 to showerhead 13 . Each flow controller 22 may include, for example, a mass flow controller or a pressure controlled flow controller. Additionally, gas supply 20 may include one or more flow modulation devices that modulate or pulse the flow of at least one process gas.

Power supply 30 includes an RF power supply 31 coupled to plasma processing chamber 10 via at least one impedance match circuit. RF power supply 31 is configured to supply at least one RF signal (RF power), such as a source RF signal and a bias RF signal, to conductive members of substrate support 11 and/or conductive members of showerhead 13 . be done. Thereby, plasma is formed from at least one processing gas supplied to the plasma processing space 10s. Accordingly, RF power source 31 may function as at least part of a plasma generator configured to generate a plasma from one or more process gases in plasma processing chamber 10 . Further, by supplying the bias RF signal to the conductive member of the substrate supporting portion 11, a bias potential is generated in the substrate W, and ion components in the formed plasma can be drawn into the substrate W. FIG.

In one embodiment, the RF power supply 31 includes a first RF generator 31a and a second RF generator 31b. The first RF generator 31a is coupled to the conductive member of the substrate support 11 and/or the conductive member of the showerhead 13 via at least one impedance matching circuit to provide a source RF signal for plasma generation (source RF electrical power). In one embodiment, the source RF signal has a frequency within the range of 13 MHz to 150 MHz. In one embodiment, the first RF generator 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are provided to conductive members of the substrate support 11 and/or conductive members of the showerhead 13 . The second RF generator 31b is coupled to the conductive member of the substrate support 11 via at least one impedance matching circuit and configured to generate a bias RF signal (bias RF power). In one embodiment, the bias RF signal has a lower frequency than the source RF signal. In one embodiment, the bias RF signal has a frequency within the range of 400 kHz to 13.56 MHz. In one embodiment, the second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. One or more bias RF signals generated are provided to the conductive members of the substrate support 11 . Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

Power supply 30 may also include a DC power supply 32 coupled to plasma processing chamber 10 . The DC power supply 32 includes a first DC generator 32a and a second DC generator 32b. In one embodiment, the first DC generator 32a is connected to a conductive member of the substrate support 11 and configured to generate the first DC signal. The generated first bias DC signal is applied to the conductive members of substrate support 11 . In one embodiment, the first DC signal may be applied to other electrodes, such as electrodes in an electrostatic chuck. In one embodiment, the second DC generator 32b is connected to the conductive member of the showerhead 13 and configured to generate the second DC signal. The generated second DC signal is applied to the conductive members of showerhead 13 . In various embodiments, at least one of the first and second DC signals may be pulsed. Note that the first and second DC generators 32a and 32b may be provided in addition to the RF power supply 31, and the first DC generator 32a may be provided instead of the second RF generator 31b. good.

The exhaust system 40 may be connected to a gas outlet 10e provided at the bottom of the plasma processing chamber 10, for example. Exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure regulating valve regulates the pressure in the plasma processing space 10s. Vacuum pumps may include turbomolecular pumps, dry pumps, or combinations thereof.

FIG. 3 is a flowchart of a substrate processing method according to one exemplary embodiment. The substrate processing method shown in FIG. 3 (hereinafter referred to as "method MT1") can be performed by the substrate processing apparatus of the above embodiment. Method MT1 may be applied to substrate W.

FIG. 4 is a partially enlarged cross-sectional view of an example substrate. As shown in FIG. 4, in one embodiment the substrate W comprises a film to be etched RE and a mask MK. A mask MK is provided on the etching target film RE.

The etching target film RE may include a recess R1. The recess R1 has sidewalls R1s and a bottom R1b. The recess R1 may be an opening. The recess R1 is, for example, a hole or trench. The recess R1 can be formed by plasma etching using the plasma processing apparatus 1, as in step ST4 described later. The etching target film RE may include a plurality of recesses R1.

The etching target film RE may include a silicon-containing film. Silicon-containing films include silicon oxide films ( _SiO2 films), silicon nitride films (SiN films), silicon oxynitride films (SiON), silicon carbide films (SiC films), silicon carbonitride films (SiCN films), organic-containing silicon It may be a single layer film of either an oxide film (SiOCH film) or a silicon film (Si film), or a laminated film containing at least two of them. The silicon-containing film may be a multilayer film in which at least two silicon-containing films are alternately arranged. A silicon nitride film (SiN film), a silicon oxynitride film (SiON film), or a silicon carbonitride film (SiCN film) is a silicon-containing film containing nitrogen. A silicon oxide film (SiO ₂ film), a silicon carbide film (SiC film), an organic-containing silicon oxide film (SiOCH film), or a silicon film (Si film) is a silicon-containing film that does not contain nitrogen. The silicon film (Si film) may be a single crystal silicon film, a polycrystalline silicon film (Poly-Si film), or an amorphous silicon film (α-Si film).

The etching target layer RE may include a germanium-containing layer. The germanium-containing film may be a single layer film of either a germanium film (Ge film) or a silicon germanium film (SiGe film). The germanium-containing film may be a laminated film including a germanium film (Ge film) and a silicon germanium film (SiGe film).

The etching target film RE may include a metal film. The metal film may contain, for example, at least one of tungsten (W), tungsten carbide (WC), aluminum (Al), titanium (Ti), titanium nitride (TiN), and ruthenium (Ru).

The etching target film RE may include an organic film. The organic film may include, for example, at least one of an amorphous carbon film (ACL) and a spin-on carbon film (SOC film: Spin On Carbon film).

The mask MK has an opening OP. A recess R1 is provided in the etching target film RE corresponding to the opening OP. The width of the opening OP can be, for example, 100 nm or less. A distance between adjacent openings OP may be, for example, 100 nm or less.

The mask MK may contain an organic film. The organic film can include at least one of a spin-on carbon film and an amorphous carbon film. When the etching target film RE includes an organic film, the mask MK may include a silicon oxide film.

The method MT1 will be described below with reference to FIGS. 3 to 8, taking as an example the case where the method MT1 is applied to a substrate W using the substrate processing apparatus of the above-described embodiment. Each of FIGS. 5-7 is a cross-sectional view illustrating one step of a substrate processing method according to one exemplary embodiment. FIG. 8 is a partially enlarged cross-sectional view of an example substrate obtained by performing a substrate processing method according to one exemplary embodiment. When the plasma processing apparatus 1 is used, the method MT1 can be executed in the plasma processing apparatus 1 by controlling each section of the plasma processing apparatus 1 by the control unit 2 . Method MT1 processes a substrate W on a substrate support 11 positioned within a plasma processing chamber 10, as shown in FIG. The substrate W may be etched by the method MT1.

As shown in FIG. 3, the method MT1 includes a step ST1, a step ST2, a step ST3, a step ST4 and a step ST5. Steps ST1 to ST5 may be performed in order. At least one of step ST3 and step ST5 may not be performed. Step ST4 may be performed simultaneously with step ST1 after step ST4. In steps ST1 to ST5, the substrate W can be processed in-situ, which is performed within the same plasma processing chamber 10 . This improves throughput. In addition, since the substrate W is not exposed to the atmosphere between each process, it is possible to perform stable processing without being affected by moisture or the like in the atmosphere. In steps ST1 to ST5, the temperature of the substrate W may be less than 30° C., 10° C. or less, or 0° C. or less. The temperature of the substrate W can be adjusted by the temperature of the substrate support 11 for supporting the substrate W. FIG. In steps ST1 and ST2, the temperature of the substrate W can be substantially the same as the temperature of the substrate supporting portion 11 . In step ST4, the temperature of the substrate W can become higher than the temperature of the substrate supporting portion 11 due to the etching.

Further, in the process ST1 to the process ST5, the substrate W is connected to the same vacuum transfer system and executed in different plasma processing chambers 10 capable of transferring the substrate W in a vacuum state, that is, so-called in-system. can be processed with As a result, the substrate W is not exposed to the atmosphere between each process, so that it is possible to perform stable processing without being affected by moisture in the atmosphere.

As shown in FIG. 5, in step ST1, the first layer F1 is formed on the sidewall R1s of the recess R1 of the substrate W using, for example, the first plasma P1. The first layer F1 may also be formed on the bottom R1b of the recess R1. The first layer F1 may be formed on a partial region of the sidewall R1s of the recess R1. In step ST1, the substrate W may be exposed to the first plasma P1. The first plasma P1 can form the first layer F1 on the sidewall R1s of the recess R1 of the substrate W. FIG. A first plasma P1 is generated from a first process gas. The first processing gas may be supplied into the plasma processing chamber 10 from the gas supply section 20 of the plasma processing apparatus 1 . The first plasma P<b>1 can be generated by the plasma generator 12 of the plasma processing apparatus 1 .

The first process gas may contain a nitrogen-containing gas. The nitrogen-containing gas may contain hydrogen. _{Nitrogen - containing gases} include _{amino groups ( -} NH ₂ ). The first process gas may contain a hydrogen-containing gas. A hydrogen-containing gas may include _H2 gas. The first process gas may be free of hydrogen halide.

The first layer F1 contains nitrogen. The first layer F1 may contain hydrogen. The first layer F1 may contain ammonia (NH ₃ ) or a compound having an amino group (—NH ₂ ). The first layer F1 is, for example, an ammonia adsorption layer. The first layer F1 is formed as a result of interaction (eg, adsorption or chemical reaction) between the first plasma P1 and the film RE to be etched.

Since ammonia (NH ₃ ) gas has high reactivity or adsorptivity, when ammonia (NH ₃ ) gas is used as the first processing gas, the side wall of the concave portion R1 of the substrate W can be removed without using the first plasma P1. Formation of the first layer F1 containing ammonia (NH ₃ ) or a compound having an amino group (—NH ₂ ) in R1s can be expected.

As shown in FIG. 6, in step ST2, a second process gas is used to form a second layer F2 on the first layer F1. Thereby, the protective film PR including the first layer F1 and the second layer F2 is formed. The second layer F2 may be formed on the sidewall R1s and the bottom R1b of the recess R1 of the substrate W. As shown in FIG. The second layer F2 is less likely to be formed in regions of the sidewall R1s and the bottom R1b of the recess R1 where the first layer F1 is not formed. In step ST2, the second plasma P2 generated from the second processing gas may be used. In step ST2, the substrate W may be exposed to the second plasma P2. The second process gas is different than the first process gas. A second process gas or a second plasma P2 can form a second layer F2 on the first layer F1. The second processing gas may be supplied into the plasma processing chamber 10 from the gas supply section 20 of the plasma processing apparatus 1 . The second plasma P2 can be generated by the plasma generator 12 of the plasma processing apparatus 1 .

The second process gas includes gas containing carbon and hydrogen. The second process gas may include at least one of hydrocarbon gas and hydrofluorocarbon gas. The hydrocarbon (C _x H _y ) gas may include at least one of CH ₄ gas and C ₂ H ₆ gas. _The hydrofluorocarbon _{( CxHyFz )} gas may include at least one of _CH2F2 gas, _CHF3 gas and _CH3F gas. When the second processing gas does not contain fluorine, unintended etching of the concave portion R1 can be suppressed.

The second layer F2 contains carbon and hydrogen. The second layer F2 is, for example, a layer of a compound having an alkyl group. The second layer F2 is formed as a result of interaction (eg, adsorption or chemical reaction) between the second plasma P2 generated from the second process gas and the first layer F1. In one example, hydrogen of amino groups of the first layer F1 can be abstracted by methyl radicals in the second plasma P2 to form N—CH ₃ bonds. Additionally, radical polymerization can cause the hydrogen of a methyl group to be abstracted by a methyl radical to form a CH ₂ —CH ₃ bond. Therefore, the protective film PR can contain alkylamine.

Depending on conditions, the second plasma P2 may not be used when the second processing gas directly interacts with the first layer F1.

Step ST2 may be performed continuously from step ST1. That is, an intermediate step such as a vacuum drawing step or a purge step may not be interposed between the step ST1 and the step ST2. When an intermediate step is interposed between step ST1 and step ST2, the processing time of the intermediate step may be 10 seconds or less. If the processing time of the intermediate step is short, the thickness uniformity of the protective film PR is improved. If the processing time of the intermediate step is long, the thickness of the protective film PR at the bottom R1b of the recess R1 tends to be larger than the thickness of the protective film PR at the sidewall R1s of the recess R1. It is considered that this is because the amount of the first layer F1 formed on the sidewall R1s of the recess R1 increases as the processing time of the intermediate step increases.

In step ST3, it may be determined whether the number of times of execution of steps ST1 and ST2 has reached a predetermined value. The determination can be made by the controller 2 of the substrate processing apparatus. When the number of execution times of the process ST1 and the process ST2 has reached a predetermined value, the process ST4 is executed. If the number of executions of steps ST1 and ST2 has not reached the predetermined value, the process returns to step ST1, and steps ST1 and ST2 are repeated. Thus, method MT1 may further include a step of repeating step ST1 and step ST2 before step ST4. Thereby, a thick protective film PR can be formed.

As shown in FIG. 7, in step ST4, for example, the third plasma P3 is used to etch the bottom R1b of the recess R1. In step ST4, the substrate W may be exposed to the third plasma P3. The third plasma P3 can etch the bottom R1b of the recess R1. A third plasma P3 is generated from a third processing gas. The third processing gas may be supplied into the plasma processing chamber 10 from the gas supply section 20 of the plasma processing apparatus 1 . The third plasma P3 can be generated by the plasma generator 12 of the plasma processing apparatus 1 . The third process gas is different than the second process gas. The third process gas may be different from the first process gas or may be the same as the first process gas.

The third process gas may contain a halogen-containing gas. A halogen-containing gas may include a fluorine-containing gas. The fluorine-containing gas may include at least one of fluorocarbon gas, hydrofluorocarbon gas, hydrogen fluoride gas, and nitrogen trifluoride ( _NF3 ) gas. The third process gas may contain a nitrogen-containing gas. Nitrogen-containing gases may include nitrogen oxide gases.

In step ST4, bias power may be applied to the substrate supporting portion 11 for supporting the substrate W. FIG. Bias power may be applied by power supply 30 in FIG. The bias power increases the etching rate of the bottom R1b of the recess R1.

As shown in FIG. 8, in step ST5, it may be determined whether the depth DP of the recess R1 has reached a threshold value. The depth DP of the recess R1 can be monitored, for example, by an endpoint monitor or the like. The determination can be made by the controller 2 of the substrate processing apparatus. If the depth DP of the recess R1 has reached the threshold, the method MT1 is terminated. If the depth DP of the recess R1 has not reached the threshold value, the process returns to step ST1, and steps ST1 to ST5 are repeated. In step ST5, it may be determined whether the number of repetitions of steps ST1 to ST5 has reached a threshold. Thus, the method MT1 may further include, after the step ST4, repeating the steps ST1, ST2, and ST4. Thereby, a deep recess R1 can be formed.

When the process ST4 is performed simultaneously with the process ST1 after the process ST4, the third plasma P3 also serves as the first plasma P1. As a result, the etching of the bottom portion R1b of the recess R1 and the formation of the first layer F1 are performed simultaneously.

When the etching target film RE includes a nitrogen-containing silicon-containing film such as a silicon nitride film, and ST1 is performed after step ST5, nitrogen contained in the silicon nitride film contributes to the formation of the first layer F1. , the first process gas may be free of nitrogen atoms. Further, when the etching target film RE is a silicon-containing film containing nitrogen and hydrogen, such as a silicon nitride film containing hydrogen atoms, a reaction product containing NH ₃ is formed on the sidewall R1s of the recess R1 by the etching in step ST4, It acts as the first layer F1. Therefore, the execution of step ST1 may be omitted after step ST5.

After the method MT1 is completed, the depth DP of the recess R1 may be 3 μm or more, and the aspect ratio of the recess R1 (the depth DP to the width WD of the recess R1) may be 30 or more.

According to the method MT1 of the above embodiment, since the protective film PR is formed on the sidewall R1s of the recess R1 in the step ST4, etching of the sidewall R1s of the recess R1 is suppressed. Therefore, it is possible to suppress the shape defect (bowing) of the side wall R1s of the recess R1 during etching.

When the temperature of the substrate W is less than 30° C. in at least one of the steps ST1 and ST2, the protective film PR can be formed at a low temperature. When the temperature of the substrate W is less than 30° C. in step ST2, a thick second layer F2 can be formed. If the temperature of the substrate W is less than 30° C. in step ST4, the recess R1 can be etched at a low temperature.

While various exemplary embodiments have been described above, various additions, omissions, substitutions, and modifications may be made without being limited to the exemplary embodiments described above. Also, elements from different embodiments can be combined to form other embodiments.

Various experiments performed for evaluation of method MT1 are described below. The experiments described below do not limit the present disclosure.

(first experiment)
In the first experiment, a substrate W including a silicon oxide film and a mask MK on the silicon oxide film was prepared. The silicon oxide film has a recess R1 provided for the opening OP of the mask MK. After that, the process ST1 was performed on the substrate W using the plasma processing system described above. In step ST1, the first processing gas is a mixed gas of hydrogen gas ( _H2 gas) and nitrogen gas ( _N2 gas). In step ST1, the first layer F1 is formed on the sidewall R1s of the recess R1 using the first plasma P1. Next, step ST2 was performed. In step ST2, the second processing gas is methane (CH ₄ ) gas. In step ST2, the second layer F2 was formed on the first layer F1 using the second plasma P2. Next, step ST1 and step ST2 were repeated until the number of execution times of step ST1 and step ST2 reached 10, respectively. In steps ST1 and ST2, the temperature of the substrate W and the substrate supporting portion 11 was -70.degree.

(Second experiment)
In the second experiment, the same method as the method of the first experiment was performed except that step ST1 was not performed.

(Results of the first experiment)
A cross-section of the recess R1 of the substrate W on which the method was performed in the first and second experiments was observed. 9 and 10 are partially enlarged cross-sectional views of substrates obtained in the first and second experiments, respectively. As shown in FIG. 9, in the first experiment, the protective film PR was formed conformally. On the other hand, as shown in FIG. 10, in the second experiment, the thickness of the protective film PR1 was uneven. The thickness of the protective film PR1 at the bottom R1b of the recess R1 was greater than the thickness of the protective film PR1 at the sidewall R1s of the recess R1.

FIG. 11 is a graph showing the thickness of the protective film obtained by executing the substrate processing method in each of the first experiment and the second experiment. In the graph, E1 and E2 indicate the results of the first and second experiments, respectively. E1s and E2s indicate the thickness of the protective film PR formed on the sidewall R1s of the recess R1 in the first and second experiments, respectively. E1b and E2b indicate the thickness of the protective film PR formed on the bottom R1b of the recess R1 in the first and second experiments, respectively.

As shown in FIG. 11, in the first experiment, the thickness of the protective film PR was 20 nm on each of the sidewall R1s and the bottom R1b of the recess R1. On the other hand, in the second experiment, the thickness of the protective film PR1 on the sidewall R1s of the recess R1 was 0 nm, and the thickness of the protective film PR1 on the bottom R1b of the recess R1 was 70 nm. Therefore, it was found that the protective film PR1 was not formed on the sidewall R1s when the step ST1 was not performed. It is considered that this is because the second layer F2 is not formed because the first layer F1 is not formed.

Further, the recesses R1 shown in FIG. 8 were formed by performing the steps ST4 and ST5 on the substrate W on which the method was performed in the first experiment and the second experiment. In order to evaluate the bowing of the side wall of the recess R1 during etching, the maximum width WD of the recess R1 was measured. The maximum value of the width WD of the recess R1 was 107 nm in the first experiment and 113 nm in the second experiment. In the first experiment, the maximum width WD of the recess R1 was smaller than in the second experiment. Therefore, in the first experiment, it was found that bowing of the side wall of the recess R1 during etching was also suppressed.

(Third experiment)
In the third experiment, the same method as the first experiment was performed except that nitrogen gas (N ₂ gas) was used as the first processing gas.

(Fourth experiment)
In the fourth experiment, the same method as the first experiment was performed except that hydrogen gas (H ₂ gas) was used as the first processing gas.

(Fifth experiment)
In the fifth experiment, the same method as the first experiment was performed except that argon gas (Ar gas) was used as the first processing gas and plasma was not generated.

(Results of the second experiment)
A cross section of the concave portion R1 of the substrate W on which the method was performed in the first experiment, the third experiment to the fifth experiment was observed. FIG. 12 is a graph showing the thickness of the protective film obtained by executing the substrate processing method in the first, third to fifth experiments. In the graph, E1 and E3 to E5 indicate the results of the first experiment and the third to fifth experiments, respectively. E3s to E5s indicate the thickness of the protective film PR formed on the sidewall R1s of the recess R1 in the third to fifth experiments, respectively. E3b to E5b indicate the thickness of the protective film PR formed on the bottom R1b of the recess R1 in the third to fifth experiments, respectively.

As shown in FIG. 12, in the third experiment, the thickness of the protective film PR was 15 nm on each of the sidewall R1s and the bottom R1b of the recess R1. On the other hand, in the fourth and fifth experiments, the thickness of the protective film PR1 on the sidewall R1s of the recess R1 was 0 nm, and the thickness of the protective film PR1 on the bottom R1b of the recess R1 was 70 nm. Therefore, it was found that the protective film PR1 was not formed on the side wall R1s when hydrogen gas or argon gas was used as the first processing gas. It is considered that this is because the second layer F2 is not formed because the first layer F1 is not formed.

(6th experiment to 10th experiment)
In the sixth experiment to the tenth experiment, the temperatures of the substrate W and the substrate supporting portion 11 in the steps ST1 and ST2 were set to −30° C., −10° C., 10° C., 30° C. and 50° C., respectively. performed the same method as

(Results of the third experiment)
A cross section of the recess R1 of the substrate W on which the method was performed in the first experiment, the sixth experiment to the tenth experiment was observed. FIG. 13 is a graph showing an example of the relationship between the thickness of the protective film and the temperature obtained by executing the substrate processing method in the first, sixth to tenth experiments. The vertical axis represents the thickness of the protective film PR at each of the sidewall R1s and the bottom R1b of the recess R1. The horizontal axis indicates the temperature of the substrate W and the substrate supporting portion 11 in the steps ST1 and ST2. In the graph, the solid line indicates the thickness of the protective film PR on the sidewall R1s of the recess R1. A dashed line indicates the thickness of the protective film PR at the bottom R1b of the recess R1. Solid and dashed lines overlap each other.

As shown in FIG. 13, in the sixth experiment, the thickness of the protective film PR was 15 nm on each of the sidewall R1s and the bottom R1b of the recess R1. In the seventh experiment, the thickness of the protective film PR was 10 nm on each of the sidewall R1s and the bottom R1b of the recess R1. In the eighth experiment, the thickness of the protective film PR on each of the sidewall R1s and the bottom R1b of the recess R1 was 5 nm. In the ninth and tenth experiments, the thickness of the protective film PR was 0 nm on each of the sidewall R1s and the bottom R1b of the recess R1. Therefore, it was found that the thickness of the protective film PR increases as the temperature of the substrate W and the substrate supporting portion 11 decreases. This is because, in step ST1, as the temperature of the substrate W and the substrate supporting portion 11 decreases, the first layer F1 is stably formed due to the increased action of adsorption or chemical reaction, and the formed first layer F1 is This is probably because the probability of resublimation is also low. Alternatively, it is conceivable that the amount of methane gas adsorbed on the first layer F1 increases in step ST2 as the temperatures of the substrate W and the substrate supporting portion 11 decrease. If, for example, methylamine or hydrazine having a boiling point higher than that of ammonia gas is used as the first processing gas, the protective film PR can be formed even when the temperature of the substrate W and the substrate supporting portion 11 is 30° C. or higher. . Alternatively, if a hydrocarbon gas having a carbon number larger than that of methane gas, for example, is used as the second processing gas, the protective film PR can be formed even when the temperature of the substrate W and the substrate supporting portion 11 is 30° C. or higher. can.

(11th experiment)
In the eleventh experiment, the same method as the first experiment was performed except that the second processing gas was used without generating the second plasma P2 in the step ST2. In step ST2, the second processing gas is methane (CH ₄ ) gas.

(Results of the fourth experiment)
A cross-section of the recess R1 of the substrate W on which the method was performed in the eleventh experiment was observed. Similar to the shape shown in FIG. 9, in the eleventh experiment, the protective film PR was formed conformally. As a result, it can be seen that the protective film PR can be formed without using the second plasma P2 in some cases. However, the thickness of the protective film PR in the eleventh experiment was thinner than the thickness of the protective film PR in the first experiment shown in FIG. From this, it can be seen that the protective film PR can be made thicker when the second plasma P2 is used than when the second plasma P2 is not used.

From the foregoing description, it will be appreciated that various embodiments of the present disclosure have been set forth herein for purposes of illustration, and that various changes may be made without departing from the scope and spirit of the present disclosure. Will. Therefore, the various embodiments disclosed herein are not intended to be limiting, with a true scope and spirit being indicated by the following claims.

2... Control part 10... Plasma processing chamber 11... Substrate support part 20... Gas supply part F1... First layer F2... Second layer MK... Mask MT1... Method OP... Opening R1... Recess , R1s... side wall, RE... film to be etched, W... substrate.

Claims (17)

A method of processing a substrate comprising a film to be etched and a mask provided on the film to be etched and having an opening, the method comprising:
(a) using a first processing gas to form a first layer containing nitrogen on sidewalls of recesses provided in the film to be etched corresponding to the openings;
(b) after (a), forming a second layer containing carbon and hydrogen on the first layer using a second process gas containing a gas containing carbon and hydrogen;
(c) after (b), etching the recess using a third process gas;
A method, including 2. The method of claim 1, further comprising repeating said (a) and said (b) before said (c). 3. The method of claim 1 or 2, further comprising, after said (c), repeating said (a), said (b) and said (c). The method according to any one of claims 1 to 3, wherein in at least one of (a) and (b), the temperature of the substrate is less than 30°C. The method according to any one of claims 1 to 4, wherein in (c), the temperature of the substrate is less than 30°C. The method of any one of claims 1 to 5, wherein (c) uses a plasma generated from the third process gas. The method of any one of claims 1 to 6, wherein (b) uses a plasma generated from the second process gas. The method of any one of claims 1 to 7, wherein (a) uses a plasma generated from the first process gas. A method according to any preceding claim, wherein the first layer contains hydrogen. 10. The method of claim 9, wherein the first layer comprises ammonia or a compound having an amino group. The method of any one of claims 1-10, wherein the first process gas comprises a nitrogen-containing gas. The method of any one of claims 1-11, wherein the second process gas comprises at least one of a hydrocarbon gas and a hydrofluorocarbon gas. The method according to any one of claims 1 to 12, wherein said film to be etched comprises at least one of a silicon-containing film and a metal film. The method of any one of claims 1 to 13, wherein in (a), (b) and (c) the substrate is treated in-situ. The method of any one of claims 1 to 13, wherein in (a), (b) and (c) the substrate is processed in-system. a chamber;
a substrate support for supporting a substrate in the chamber, the substrate comprising a film to be etched and a mask provided on the film to be etched and having an opening;
a gas supply configured to supply each of a first process gas, a second process gas, and a third process gas into the chamber, wherein the second process gas includes a carbon- and hydrogen-containing gas; , a gas supply, and
a control unit;
with
The control unit controls the gas supply unit to form a nitrogen-containing first layer using the first processing gas on sidewalls of recesses provided in the etching target film corresponding to the openings. is configured to
The control unit controls the gas supply unit to form a second layer containing carbon and hydrogen on the first layer using the second process gas after forming the first layer. configured to
The substrate processing apparatus, wherein the control unit is configured to control the gas supply unit to etch the recess using the third process gas after forming the second layer. A method of processing a substrate comprising a film to be etched and a mask provided on the film to be etched and having an opening, the method comprising:
(a) a step of exposing the substrate to a first processing gas, the first processing gas forming a first layer containing nitrogen on sidewalls of recesses provided in the etching target film corresponding to the openings; Formable, a process;
(b) after (a), exposing the substrate to a second process gas, the second process gas including a gas containing carbon and hydrogen, and forming a second layer containing carbon and hydrogen; formable on the first layer; and
(c) after (b), exposing the substrate to a third process gas, wherein the third process gas is capable of etching the recess;
A method, including

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